This invention relates generally to electrostatographic printing machines, and more particularly the invention is directed to a reproduction machine having a transfix-like preconditioning assembly for preheating and pre-stressing a copy sheet material in order to stabilize its size before it undergoes heat pressure stressing in image receiving and fusing transfix nips of the machine.
In an electrostatographic printing machine, a photoconductive member is charged to a substantially uniform potential to sensitize the surface thereof. The charged portion of the photoconductive member is exposed to a light image of an original document being reproduced. Exposure of the charged photoconductive member selectively dissipates the charge thereon in irradiated areas. This records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document being reproduced.
After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing developer material containing charged toner particles, for example, black toner particles, into contact therewith. Developer material can be single component comprising only of charged toner particles, or it may be dual component comprising carrier particles and toner particles that are triboelectrically charged when admixed or mixed with the carrier particles. In either case, bringing the developer material into contact with the latent image forms a toner image on the photoconductive member, which is subsequently transferred to a copy sheet. The copy sheet is then separated from the photoconductive member and the toner powder is fed on the copy sheet through a fusing apparatus where it is heated to permanently affix it to the copy sheet, thus forming a black and white copy of the original document. Alternatively, the transfer and fixing steps can be performed simultaneously, usually by a combination of heat, pressure and electrostatic fields. This technique is called transfix.
Multi-color electrostatographic printing machines which use multi-colored toners are substantially identical in each color image forming process to the foregoing process of black and white printing which uses only black toner. However, rather than forming a single latent image on the photoconductive surface, several single color latent images corresponding to color separated light images of the original document are recorded thereon. Each single color electrostatic latent image is developed with toner particles of a color complementary thereto. This process may be performed in a single pass, or in multipasses during which image formation is repeated a plurality of cycles for differently colored images using their respective complementarily colored toner particles to form color toner images. The process may also be carried out in a tandem arrangement with each different color toner image being transferred in registration onto an intermediate transfer belt. Each single color toner powder image may also be transferred or transfixed as such onto a copy sheet in superimposed registration with the other toner powder images.
In a non-transfix machine, a composite multi-layered toner powder image is created and transferred onto a copy sheet. The copy sheet is then separated from the photoconductive member and. thereafter, the multi-layered toner powder image on the sheet is fed through a fusing apparatus and permanently affixed to the copy sheet, thus creating a color copy of the original multi-color document. In a black and white or multi-color electrostatographic printing machine, the copy sheet is typically brought into moving contact with the photoconductive member during toner powder image transfer to the copy sheet. In a non-transfix machine, a sheet transport apparatus is typically provided for receiving the copy sheet incrementally as it is incrementally separated from the photoconductive member, and for transporting the copy sheet towards and into a fusing apparatus where the toner powder image is heated in order to fuse and permanently affix the powder image to the copy substrate.
Unfortunately, it has been found that when copy sheet paper is subjected to the temperatures and pressures of fusing or transfixing apparatus in a multicolor tandem machines, the copy sheet of paper, and the image it might convey, tends to experience a significant change in size. This creates an image registration problem if subsequent separations of an image are transfixed to a paper copy sheet, inasmuch as their size will vary unpredictably.